全文获取类型
收费全文 | 79167篇 |
免费 | 6502篇 |
国内免费 | 5037篇 |
专业分类
化学 | 23346篇 |
晶体学 | 1807篇 |
力学 | 3525篇 |
综合类 | 346篇 |
数学 | 18526篇 |
物理学 | 43156篇 |
出版年
2022年 | 160篇 |
2021年 | 313篇 |
2020年 | 626篇 |
2019年 | 936篇 |
2018年 | 896篇 |
2017年 | 603篇 |
2016年 | 444篇 |
2015年 | 402篇 |
2014年 | 1065篇 |
2013年 | 1646篇 |
2012年 | 1148篇 |
2011年 | 1710篇 |
2010年 | 2319篇 |
2009年 | 6829篇 |
2008年 | 7908篇 |
2007年 | 6372篇 |
2006年 | 5812篇 |
2005年 | 3967篇 |
2004年 | 3770篇 |
2003年 | 4000篇 |
2002年 | 4717篇 |
2001年 | 3682篇 |
2000年 | 3490篇 |
1999年 | 3315篇 |
1998年 | 2742篇 |
1997年 | 1909篇 |
1996年 | 1723篇 |
1995年 | 2200篇 |
1994年 | 2138篇 |
1993年 | 1596篇 |
1992年 | 1101篇 |
1991年 | 833篇 |
1990年 | 679篇 |
1989年 | 601篇 |
1988年 | 568篇 |
1987年 | 405篇 |
1986年 | 193篇 |
1985年 | 945篇 |
1984年 | 619篇 |
1983年 | 489篇 |
1982年 | 640篇 |
1981年 | 792篇 |
1980年 | 721篇 |
1979年 | 560篇 |
1978年 | 581篇 |
1977年 | 539篇 |
1976年 | 542篇 |
1975年 | 317篇 |
1974年 | 354篇 |
1973年 | 463篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
101.
Akkaraboyina Lakshmi Lavanya K. Gowri Bala Kumari K. R. S. Prasad Pradeep Kumar Brahman 《Electroanalysis》2021,33(3):591-600
In this work, an economically viable, very low cost, indigenous, ubiquitously available electrochemical sensor based on bimetallic nickel and tungsten nanoparticles modified pencil graphite electrode (NiNP-WNP@PGE) was fabricated for the sensitive and selective detection of bisphenol A (BPA). The NiNP-WNP@PGE sensor was prepared by a facile electrochemical one step co-deposition method. The prepared nanocomposite was morphologically characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), electrochemically by cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The proposed sensor displayed high electrocatalytic activity towards electro-oxidation of BPA with one irreversible peak. The fabricated sensor displayed a wide detection window between 0.025 μM and 250 μM with a limit of detection of 0.012 μM. PGE sensor was successfully engaged for the detection of BPA in bottled water, biological, and baby glass samples. 相似文献
102.
Dr. Vinayak Adimule R. G. Revaiah Santosh S. Nandi Adarsha Haramballi Jagadeesha 《Electroanalysis》2021,33(3):579-590
In the present work, Cr doped tellurium dioxide nanostructures (CTO NS)(1 wt %, 6 wt %, 8 wt % and 12 wt %) synthesized by co precipitation method and characterized by CV, UV-Visible, SEM, XRD, XPS spectroscopic analysis. Electron beam deposited thin film of CTO NS having 12 wt % of Cr exhibited EGFET-pH sensitivity of 62.03 mV/pH at 250 °C in buffer solutions of pH 6–12, linearity 0.9345, drift rate of 1.12 mV/h and deviation of 0.01145 as compared with 1 wt %, 6 wt % and 8 wt % of CTO NS. 相似文献
103.
Daniela Nunes da Silva Hanna Leijoto de Oliveira Keyller Bastos Borges Arnaldo César Pereira 《Electroanalysis》2021,33(2):506-514
The analysis of 17β-estradiol with high sensitivity and selectivity is extremely relevant to control the impacts that this compound can cause on health and the environment. Thus, we describe the development and application of a magneto carbon paste electrode based on magnetic molecularly imprinted polymer (MCPE-MMIP) for determination of 17β-estradiol. The analyte adsorbed on the MMIP was immobilized on the electrode surface by magnetic capture. The morphological and structural characterization of the obtained MMIP suggests that the material was effectively synthesized. MCPE-MMIP showed an improvement in the sensitivity for 17β-estradiol detection when compared to electrode configurations in the absence of this material. The optimum conditions (0.10 mol L−1 phosphate buffer pH 7.0) were reached by differential pulse adsorptive stripping voltammetry (DPAdSV), in which the method presented linearity ranged from 0.06 to 175 μmol L−1 with limits of detection and quantification of 0.02 and 0.06 μmol L−1, respectively. The proposed sensor was applied effectively in the analysis of 17β-estradiol in river water and raw milk samples, exhibiting excellent recovery values (between 96.20 and 104 %), which were confirmed by HPLC analysis. 相似文献
104.
该文建立了大孔树脂-高速逆流色谱分离薇甘菊中黄酮类物质的方法。分离条件为:采用大孔树脂AB-8,洗脱液为50%(v/v)乙醇水溶液,高速逆流色谱溶剂体系为正丁醇-乙酸-水(4:1:5,v/v)。从薇甘菊中分离到4种黄酮类物质:槲皮素-3-O-芸香糖苷(纯度90.2%)、山奈酚-3-O-芸香糖苷(纯度98.55%)、木犀草苷(纯度98.33%)和紫云英苷(纯度99.23%)。建立的大孔树脂-高速逆流色谱方法简单、高效,可扩展应用于从其他植物中分离黄酮类物质。 相似文献
105.
《Electroanalysis》2017,29(4):1188-1196
In this work, one novel electrochemical sensor was prepared by alternative deposition of phosphomolybdic acid (PMoA) and poly(ethyleneimine) (PEI) on an indium tin oxide glass substrate through layer‐by‐layer assembly. The performance of as‐prepared electrode was evaluated with both of oxidizing compounds of iodate and H2O2 and reducing compounds of dopamine and ascorbic acid as models. The results showed that corresponding current response of redox peak increased linearly with the concentration of above compounds increasing in certain ranges, respectively. Limits of detection to them were in the range of 1.0×10−4 ‐ 4.3×10−4 mg mL−1 with cyclic voltammetry (CV) in 0.1 mol L−1 NaAc‐HAc buffer (pH 5.0). The electrode showed high stability and remained 95 % of its initial activity even after 100 cycles of CV scan. When applied in real samples of table salts, juice and human serum, high recoveries of 96.84 to 100.33 % were achieved with relative standard deviations of 1.11‐3.96 % (n=3) at three spiked levels. Moreover, it was also successfully applied for the simultaneous determination of dopamine and ascorbic acid in human serum with differential pulse voltammetry. The results indicated that PMoA/PEI multilayer modified electrode can be used as a universal electrochemical sensor for sensitive detection of redox compounds. 相似文献
106.
ABSTRACTA repeat unit of cell wall teichoic acids (WTA) isolated from E. faecium U0317 was chemically synthesized efficiently by a stepwise strategy. It was derivatized with a 5-aminopentanyl linker to facilitate conjugation with carrier proteins KLH and HSA. Immunological studies of the KLH conjugate 1 demonstrated that it could provoke robust immune responses and high titers of IgG antibodies, which could successfully recognize the synthesized WTA repeat unit 3. This result suggested that synthetic glycoconjugate 1 could be a promising vaccine candidate against E. faecium for further studies. 相似文献
107.
Santosh Ramdas Borkar Naveen Bokolia Indrapal Singh Aidhen Inshad Ali Khan 《Tetrahedron: Asymmetry》2017,28(1):186-195
A series of threo- and erythro-configured open-chain trihydroxy ketones was synthesized starting from l- and d-ascorbic acid respectively as the starting material, through the use of Grignard reactions for the requisite CC bond formations. The lipophilic ketones were screened against Mycobacteriumtuberculosis for anti-proliferative activity. The lipophilic ketones with tetradecyl alkyl side chains were found to be moderately active against cell proliferation. 相似文献
108.
109.
110.